1. The yoke of a d.c. machine is made of (i) silicon steel (ii) soft iron (iii) aluminium (iv) cast steel 2. The armature of a d.c. machine is made of (i) silicon steel (ii) wrought iron (iii) cast steel (iv) soft iron 3. The coupling field between electrical and mechanical systems of a d.c. […]
1. An ammeter is …………… instrument. (i) an indicating (ii) an integrating (iii) a recording (iv) none of the above 2. The controlling torque of an indicating instrument ………. as the deflection of the moving system increases. (i) remains unchanged (ii) decreases (iii) increases (iv) none of the above 3. When the pointer of an
Electrostatic voltmeters are based on the fact that an electric force (attraction or repulsion) exists between charged plates or objects. An electrostatic voltmeter is essentially an air condenser ; one plate is fixed while the other, which is coupled to the pointer, is free to rotate on jewelled bearings. Electrostatic Voltmeter Working Principle When p.d.
1. In Fig. given below, the magnetic circuit is the path (i) DAB (ii) ABCDA (iii) ABC (iv) ABCD 2. If l is the magnetic path in the above Fig., then magnetising force is (i) Nl (ii) Nl x l (iii) l ÷ NI (iv) NI ÷ l 3. The reluctance of the magnetic circuit
1. The force between two electrons separated by a distance r varies as (i) r2 (ii) r (iii) r-1 (iv) r-2 2. Two charges are placed at a certain distance apart. A brass sheet is placed between them. The force between them will (i) increase (ii) decrease (iii) remains unchanged (iv) none of the above
1. A kilowatt hour is the unit of (i) energy(ii) power(iii) electric charge(iv) electric current 2. Heat produced in a conductor depends (i) inversely on time(ii) directly on time(iii) both (i) and (ii)(iv) none of the above 3. If potential difference across a conductot of a material of resistivity ρ remains constant, then heat produced
Slip rings are often overlooked aspects of machines that have a rotary part to it and need a transmission of electrical signal or power. Without slip rings, rotational devices and machines might not operate as smoothly as they do today, and that’s why slip rings can be seen in so many devices across so many
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1. The diameter of an atom is about (i) 10-10 m (ii) 10-8m (iii) 10-2 m (iv) 10-15 m 2. The number of compounds available in nature is (i) 105 (ii) 300 (iii) 1000 (iv) unlimited 3. The mass of a proton is …….. the mass of electron. (i) equal to (ii) less than (iii)
Most insulations fail during one of the following events: Switching overvoltage due to the inductive and capacitive energy of the system overshooting the system voltage that can be as high as 2 × rated voltage. This is analogous to overpressure due to water hammer when a water pipe is suddenly shut off (switched-off). Lightning overvoltage
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The fuse provides protection by melting away a thin metal link in the faulted circuit. The metal link may be of silver, copper, or nickel, silver being more common for long-term performance stability. The fuse body is generally filled with a sand-type filler (Figure 1) to suppress sparks when the fuse link melts and interrupts the